In the field of gravity powered part transfer systems, applications arise which require speed control or retardation systems in which it is desired that the speed of movement be reasonably constant even though the mass being controlled is variable. One such type of application is shown in my copending patent application, Ser. No. 176,562, filed Aug. 8, 1980, now U.S. Pat. No. 4,316,535, issued Feb. 23, 1982. A type of device which is particularly suitable for creating a retardation force or torque proportional to the velocity of movement employs a viscous fluid operating in shear between a fixed housing and a movable rotor.
Such devices generally have a fixed ratio of torque to velocity which can be altered only by changing the viscosity of the fluid or the geometrical properties of the device. In applications such as my aforesaid copending application, where the applied load is created by a mass rolling down an inclined slope, the velocity will be approximately proportional to the mass. It is one object of this invention to provide a system in which the retardation is approximately proportional to the mass being supported, whereby the velocity reached is approximately constant, independent of mass.
In another copending patent application, Ser. No.327,515, filed Dec. 4, 1981, now U.S. Pat. No. 4,497,393 an invention is disclosed for a viscous retardation device which requires no moving seals, and in which the viscous fluid is contained in a chamber, a portion of which is a flexible membrane. It is another object of this invention to incorporate this hermetic sealed fluid enclosure with the weight responsive retardation system.
Other objects and features of the invention will be apparent in the following description and claims in which the principles of the invention are set forth together with details of the structure to enable those skilled in the art to practice the invention, all in connection with the best mode presently contemplated for the invention.